JSF 2 PreRenderViewEvent example

程序员文章站 2022-07-14 13:38:08

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为什么80%的码农都做不了架构师？>>> JSF 2 PreRenderViewEvent example

In JSF 2.0, you can attach a javax.faces.event.PreRenderViewEvent system event to perform custom task before a view root (JSF page) is display.

Let see a complete PreRenderViewEvent example below :

1. Managed Bean

Create a normal bean, contains a method signature “public void method-name(ComponentSystemEvent event)“, later you will ask listener to call this method.

In this method, it validate “role” in the current session, if the role is NOT equal to “admin“, then navigate it to outcome “access-denied“.

package com.mkyong;  import javax.faces.application.ConfigurableNavigationHandler; import javax.faces.bean.ManagedBean; import javax.faces.bean.SessionScoped; import javax.faces.context.FacesContext; import javax.faces.event.ComponentSystemEvent;  
@ManagedBean(name="user") @SessionScopedpublic class UserBean{  
  public void isAdmin(ComponentSystemEvent event){  
	FacesContext fc = FacesContext.getCurrentInstance();  
	if (!"admin".equals(fc.getExternalContext().getSessionMap().get("role"))){  
		ConfigurableNavigationHandler nav 
		   = (ConfigurableNavigationHandler) 
			fc.getApplication().getNavigationHandler();  
		nav.performNavigation("access-denied"); 	}		
  }	}

2. JSF Page

Now, you use f:event tag to attach “preRenderView” system event to “default.xhtml” page.

default.xhtml

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"          xmlns:h="http://java.sun.com/jsf/html"       xmlns:f="http://java.sun.com/jsf/core"       >  
 	<f:event listener="#{user.isAdmin}" type="preRenderView" />  
	<h:body>  
	    <h1>JSF 2 protected page example</h1>  
	</h:body>  </html>

access-denied.xhtml

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"          xmlns:h="http://java.sun.com/jsf/html"       >  
    <h:body>  
    	<h1>Access Denied!</h1>  
    </h:body>  </html>